Cisco Support Community
Community Member

rdundant switch an mac

Hi dears,

A customer of mine wants to use two interconnected clatalyst 4500R switch on a redundant industrial network. One computer is connected to a 2800 switch that is connected to both 4500R. On the otherside of the network, a PLC is also connected to a 2800 that also connect to both 4500R.

I know that spanning tree protocol will prevent the loops and close redundant port. In case of failure of a network device, then the redundant port will be opened and the traffic will pass through this new route.

What I want to know is on wich OSI level this works. how does the switch sees that traffic can not be forwarded. We do not use TCP/IP for our connection, but directly mac adresses, will this trafic also be routed to the correct adress in case of failure?

Thanks for your help

Community Member

Re: rdundant switch an mac


STP works on layer 2 of the OSI reference model. It works on the basis of mac-addresses of the bridges/switches and there are packets called BPDU's( Bridge Protocol Data Unit) which are exchanged between the switches and have information which leads to the STP process completion.

STP process puts redundant paths into blocking mode and in case of failure of the primary path, stp process is again calculated to open up the blocking port.

Please find below the link which would give you further clarity on the STP process.


Community Member

Re: rdundant switch an mac

Community Member

Re: rdundant switch an mac

Thank you so much for your help. It seems that I can not follow the link with my account. Anyway, your answer was very helpfull, thanks again.

CreatePlease to create content